Melanotan I (Afamelanotide)

Melanocortin receptor pharmacology

Melanocortin receptors are a family of five G-protein-coupled receptors whose native ligands are the POMC-derived peptides. Melanotan I is used as a stable probe of that system: the Nle⁴ and D-Phe⁷ substitutions were reported to raise resistance to proteolysis and prolong receptor occupancy compared with native α-MSH, which makes cAMP-accumulation assays and receptor-binding studies easier to run over longer time courses.

Melanogenesis in cell and tissue models

Photobiology and UV-response research

Where it differs from Melanotan II

Melanotan II is a shortened cyclic heptapeptide with broad melanocortin activity, including MC3R and MC4R. Melanotan I keeps the full linear backbone and is described as more MC1R-weighted. Comparative studies therefore often run the two side by side to separate pigment-pathway effects from the wider central melanocortin effects reported for the cyclic analog.

Analytical profile

Material is produced by solid-phase synthesis, purified by preparative reverse-phase chromatography and released against an HPLC purity specification with mass-spectrometric identity confirmation. Water content and net peptide content are worth noting when normalising stock concentrations between lots.

Let the vial equilibrate to room temperature before opening so that moisture does not condense onto the cake. Add bacteriostatic or sterile water slowly down the inner wall rather than directly onto the powder, then swirl gently until clear — vigorous shaking encourages aggregation and foaming. Record the exact diluent volume so stock concentration is traceable, then aliquot into single-use vials to avoid repeated freeze–thaw cycles. Keep aqueous stocks refrigerated and shielded from light, since the tryptophan and tyrosine residues are photosensitive. Store unopened lyophilate at −20 °C and log the lot number against your COA.